(1) Field of the Invention
The present invention relates to a method of and an apparatus for producing diamond thin films. More particularly the present invention relates to a method of producing diamond thin films having uniform film thickness and excellent adhesion, as well as an apparatus for producing diamond thin film.
(2) Description of the Related Art
Since diamond films or diamond-like carbon films (i-carbon etc.) are excellent in hardness, abrasion resistance, electric insulation, heat conductivity and solid lubricancy, they have been utilized, for example, as hard coating material for various members such as cutting tools, abrasion-resistant machinery parts, as well as electronic material.
As a method of producing diamond thin films, a vapor phase method has generally been used.
A method of manufacturing diamond films has been disclosed in, for example, Japanese Patent Application Laid-Open 63-166733, which comprises placing a substrate on which metal or metal compound is uniformly scattered in a reaction vessel, heating the vessel to 500.degree.-1300.degree. C., then introducing a gas, for forming a diamond film at least containing hydrogen atoms, carbon atoms and oxygen atoms into the reaction vessel and activating the gas to thereby deposit the diamond film on the surface of the substrate.
In this method, however, since the substrate on which diamond films are to be formed is placed on a flat support table, when the diamond forming gas is activated, for example, by means of microwaves or high frequency waves, plasmas are locally concentrated on the edges of the substrate protruding on the support table, for example, ridge lines, especially corners of the substrate.
If a cutting tool coated with diamond thin films is produced by using the above-mentioned method, plasmas are locally concentrated on the edges of the cutting tool. Since the thickness of the film is abnormally increased in these portions which makes the film thickness not uniform abrupt changes of thermal stresses or inner stresses are caused. Therefore, it is only possible to obtain a cutting tool coated with a diamond thin film of poor durability in which the diamond thin film is liable to be exfoliated at the cutting portion which is most important to the cutting tool.
Japanese Patent Application Laid-Open 63-285192 also discloses a method of synthesizing a diamond film by means of a vapor phase process using a carbon source compound and a hydrogen source compound, in which the carbon source compound and the hydrogen source compound are partially or entirely preheated before excitation.
However, in this method, since the substrate on which the diamond film is to be formed is also placed on a flat support table, when the carbon source compound and the hydrogen source compound are excited, for example, by means of microwaves or high frequency waves, the foregoing problem of local concentration of plasmas is also present.
That is, a conventional method of producing a diamond film using the vaper phase method, particularly, by means of a method involves a problem that the plasmas are locally concentrated on the edges and, most of all, it is difficult to produce a diamond film of excellent uniform film thickness causing less exfoliation by means of a microwave plasma method or a high frequency wave plasma method causing plasma heat evolution of the substrate by plasma.